U.S. patent number 4,467,323 [Application Number 06/327,732] was granted by the patent office on 1984-08-21 for engine analyzer with simulated analog meter display.
This patent grant is currently assigned to Bear Automotive Service Equipment Company. Invention is credited to Michael J. Kling, Joseph A. Marino.
United States Patent |
4,467,323 |
Kling , et al. |
August 21, 1984 |
Engine analyzer with simulated analog meter display
Abstract
An engine analyzer for an internal combustion engine includes
circuitry, under the control of a microprocessor, which senses
parameters of operation of the internal combustion engine and
supplies digital signals indicative of those sensed parameters. A
raster scan cathode ray tube (CRT) display is controlled by the
microprocessor to display a simulation of an analog meter having a
pointer or needle which moves as a function of the digital signals.
When an analog display, such as a tachometer, is selected, the
microprocessor controls the raster scan CRT to display a visual
depiction of a meter having the appropriate range of values and
having a needle which moves according to the measurements made by
the system. The microprocessor automatically changes the scale of
the simulated meter as appropriate without operator intervention.
When operation within a predetermined range of values is required,
the microprocessor causes the raster scan CRT display to produce a
shaded area representing the range within which the needle should
remain.
Inventors: |
Kling; Michael J. (Mequon,
WI), Marino; Joseph A. (Waukesha, WI) |
Assignee: |
Bear Automotive Service Equipment
Company (Milwaukee, WI)
|
Family
ID: |
23277802 |
Appl.
No.: |
06/327,732 |
Filed: |
December 4, 1981 |
Current U.S.
Class: |
345/24;
345/440.1; 701/102 |
Current CPC
Class: |
G01M
15/02 (20130101); G01R 13/40 (20130101); G01P
1/08 (20130101) |
Current International
Class: |
G01P
1/08 (20060101); G01R 13/40 (20060101); G01P
1/00 (20060101); G01M 15/02 (20060101); G01R
13/00 (20060101); G09G 001/00 () |
Field of
Search: |
;364/550,551 ;73/117.3
;324/115,96,379,384
;340/715,721,722,727,734,745,706,753,754,720 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Krass; Errol A.
Assistant Examiner: Tager; Clifford L.
Attorney, Agent or Firm: Kinney & Lange
Claims
What is claimed is:
1. An engine analyzer for testing systems and components of an
internal combustion engine under test conditions, the engine
analyzer comprising:
means for supplying a variable input electrical signal derived from
the system of component of the internal combustion engine under a
test condition;
means for periodically converting the input electrical signal to a
digital signal;
point addressable cathode ray tube (CRT) display means for
displaying visual information based upon control signals; and
digital control means for supplying the control signals to the CRT
display means to cause the CRT display means to display a simulated
analog meter including a visual depiction of a scale and a visual
depiction of a pointer, the pointer having a position with respect
to the scale which is controlled and updated periodically by the
digital control means as a function of the digital signal to
provide a simulated analog representation of variation of the
variable input electrical signal.
2. The engine analyzer of claim 1 wherein the digital control means
periodically provides control signals to the CRT display means
representative of a first variable end point of the pointer as a
function of the digital signal, a second fixed end point, and
intermediate points between the first and second end points.
3. The engine analyzer of claim 1 wherein the control signals from
the digital control means include digital data representative of
individual points of the point addressable CRT display means, and
wherein the point addressable CRT display means comprises:
display memory means for periodically storing the digital data from
the digital control means; and
a point of addressable CRT display for displaying visual
information based upon the stored digital data.
4. The engine analyzer of claim 3 wherein the display memory means
periodically stores digital data representative of the visual
information being displayed and digital data representative of
visual information to replace the visual information being
displayed.
5. The engine analyzer of claim 4 wherein the digital control means
periodically provides control signals which cause the point
addressable CRT display to erase the visual information based upon
the first set of digital data while writing the visual information
based upon the second set of digital data.
6. The engine analyzer of claim 1 wherein the digital control means
selects one of a plurality of scales based upon a magnitude of the
digital signal and supplies control signals which cause the visual
depiction of the selected scale to be produced by the CRT display
means.
7. The engine analyzer of claim 1 wherein the digital control means
further periodically supplies control signals to the point
addressable CRT display means to cause the point addressable CRT
display means to display an alphanumeric message which includes a
numerical representation of a magnitude of the digital signal in
addition to the visual depiction of the scale and the visual
depiction of the pointer.
8. The engine analyzer of claim 1 wherein the digital control means
further supplies control signals to the point addressable display
CRT means to cause the point addressable CRT display means to
display a shaded area representative of a range withinn which the
pointer should be maintained in order to maintain the test
condition.
9. The engine analyzer of claim 8 wherein the shaded area and the
cursor are displayed by the point addressable CRT display means
independent of one another so that the pointer can move within and
outside of the shaded area as a function of the digital signal.
10. An engine analyzer for testing systems and components of an
internal combustion engine under test conditions, the engine
analyzer comprising:
means for supplying a variable input electrical signal derived from
the system or component of the internal combustion engine under a
test condition;
means for periodically converting the input electrical signal to a
digital signal;
display memory means for storing digital data representative of
individual image points;
a point addressable display for displaying visual information based
upon the stored digital data; and
digital control means for periodically supplying the digital data
to the display memory means to cause the point addressable display
to display a simulated analog meter including a visual depiction of
a scale and a visual depiction of a pointer, the pointer having a
position with respect to the scale which is controlled and updated
periodically by the digital control means by means of the digital
data as a function of the digital signal to provide a simulated
analog representation of variation of the variable input electrical
signal.
11. The engine analyzer of claim 10 wherein the digital data
includes a first variable end point of the pointer which is a
function of the digital signal, a second fixed end point, and
intermediate points between the first and second end points.
12. The engine analyzer of claim 10 wherein the display memory
means periodically stores digital data representative of the visual
information being displayed and digital data representative of
visual information to replace the visual information being
displayed.
13. The engine analyzer of claim 12 wherein the digital control
means periodically provides control signals which cause the point
addressable display to erase the visual information based upon the
first set of digital data while writing the visual information
based upon the second set of digital data.
14. The engine analyzer of claim 10 wherein the digital control
means selects one of a plurality of scales based upon a magnitude
of the digital signal and supplies digital data which cause the
visual depiction of the selected scale to be produced.
15. The engine analyzer of claim 10 wherein the digital data from
the digital control means further includes points which cause the
point addressable display means to display an alphanumeric message
which includes a numerical representation of a magnitude of the
digital signal.
16. The engine analyzer of claim 10 wherein the digital data from
the digital control means further includes points which cause the
point addressable display means to display a shaded area
representative of a range within which the pointer should be
maintained in order to maintain the test condition.
17. The engine analyzer of claim 16 wherein the shaded area and the
pointer are displayed by the point addressable display independent
of one another so that the pointer can move within the outside of
the shaded area as a function of the digital signal.
18. An engine analyzer for testing systems and components of an
internal combustion engine under test conditions, the engine
analyzer comprising:
means for supplying a variable input electrical signal derived from
the system or component of the internal combustion engine under a
test condition;
means for periodically converting the input electrical signal to a
digital signal;
point addressable display means for displaying visual information
based upon control signals; and
digital control means for supplying the control signals to the
point addressable display means to cause the point addressable
display means to display a simulated analog meter including a
visual depiction of a scale and a visual depiction of a pointer,
and a shaded area representative of a range within which the
pointer should be maintained in order to maintain the test
condition, the pointer having a position with respect to the scale
which is controlled and updated periodically by the digital control
means as a function of the digital signal to provide a simulated
analog representation of variation of the variable input electrical
signal.
19. The engine analyzer of claim 18 wherein the shaded area and the
pointer are displayed by the point addressable display means
independent of one another so that the pointer can move within and
outside of the shaded area as a function of the digital signal.
20. The engine analyzer of claim 18 wherein the digital control
means periodically provides control signals to the point
addressable display means representative of a first variable end
point of the pointer as a function of the digital signal, a second
fixed end point, and intermediate points between the first and
second end points.
21. The engine analyzer of claim 18 wherein the control signals
from the digital control means include digital data representative
of individual points of the point addressable display means, and
wherein the point addressable display means comprises:
display memory means for periodically storing the digital data from
the digital control means; and
a point addressable display for displaying visual information based
upon the stored digital data.
22. The engine analyzer of claim 21 wherein the display memory
means periodically stores digital data representative of the visual
information being displayed and digital data representative of
visual information to replace the visual information being
displayed.
23. The engine analyzer of claim 22 wherein the digital control
means periodically provides control signals which cause the point
addressable display to erase the visual information based upon the
first set of digital data while writing the visual information
based upon the second set of digital data.
24. An engine analyzer for testing systems and components of an
internal combustion engine under test conditions, the engine
analyzer comprising:
means for supplying a variable input electrical signal derived from
the system or component of the internal combustion engine under a
test condition;
means for periodically converting the input electrical signal to a
digital signal;
point addressable display means for displaying visual information
based upon control signals; and
digital control means for supplying the control signals to the
point addressable display means to cause the point addressable
display means to display a simulated analog meter including a
visual depiction of a selected scale of a plurality of scales and a
visual depiction of a pointer, the pointer having a position with
respect to the selected scale which is controlled and updated
periodically by the digital control means as a function of the
digital signal to provide a simulated analog representation of
variation of the variable input electrical signal, the digital
control means selecting the selected scale based upon a magnitude
of the digital signal.
25. An engine analyzer for testing systems and components of an
internal combustion engine under test conditions, the engine
analyzer comprising:
means for supplying a variable input electrical signal derived from
the system or component of the internal combustion engine under a
test condition;
means for periodically converting the input electrical signal to a
digital signal;
point addressable display means for displaying visual information
based upon control signals; and
digital control means for supplying the control signals to the
point addressable display means to cause the point addressable
display means to display a simulated analog meter including a
visual depiction of a scale, a visual depiction of a pointer and a
message, the pointer having a position with respect to the scale
which is controlled and updated periodically by the digital control
means as a function of the digital signal to provide a simulated
analog representation of variation of the variable input electrical
signal, wherein the message is a function of the digital signal and
includes a numerical value which corresponds to a reading being
displayed by the simulated analog meter.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
Reference is hereby made to the following copending applications,
which were filed on even date with the present application and are
assigned to the same assignee as the present application: ENGINE
ANALYZER WITH DIGITAL WAVEFORM DISPLAY, J. Marino, M. Kling and S.
Roth Ser. No. 327,734; ENGINE ANALYZER WITH CONSTANT WIDTH DIGITAL
WAVEFORM DISPLAY, J. Marino, and M. Kling Ser. No. 327,511, and now
U.S. Pat. No. 4,399,407; and IGNITION COIL TEST APPARATUS, J.
Marino, M. Kling, S. Roth and S. Makhija Ser. No. 327,733.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to engine analyzer apparatus used for
testing internal combustion engines.
2. Description of the Prior Art
One common type of engine analyzer apparatus used for testing an
internal combustion engine employs a cathode ray tube having a
display screen on which analog waveforms are displayed which are
associated with operation of the engine. In a typical apparatus of
this type, a substantially horizontal trace is produced on the
screen of the cathode ray tube by applying a sawtooth ramp voltage
between the horizontal deflection plates of the tube while the
analog signal being measured is applied to the vertical deflection
plates of the tube. The typical analog signals which are applied to
the vertical plates of the cathode ray tube are the primary voltage
which exists across the primary winding of the ignition coil, and a
signal representative of the secondary voltage of the ignition
coil. These voltages are affected by the condition of various
elements of the ignition system of the engine, such as the spark
plugs.
With the advent of low cost microelectronic devices, and in
particular microprocessors, digital electronic systems have found
increasing use in a wide variety of applications. Digital
electronic systems have many significant advantages over analog
systems, including increased ability to analyze and store data,
higher accuracy, greater flexibility in design and application, and
the ability to interface with computers having larger and more
sophisticated data processing and storage capabilities. In the
past, some engine analyzer systems have been proposed which utilize
microprocessors and digital circuitry to control some of the
functions of the engine analyzer apparatus. In these prior art
systems, however, the waveform display function of the engine
analyzer apparatus has remained essentially an analog electrical
function, even when the systems utilize microprocessors and digital
electronics for other functions.
Engine analyzers also typically include a number of analog panel
meters wich are used to display other operating parameters which
are measured by the engine analyzer. One example of an analog panel
meter used in prior art engine analyzers is a tachometer. Even in
the engine analyzer systems using microprocessors and digital
circuitry, analog panel meters have continued to be used. For
example, an analog display of engine rpm is far more meaningful
than a digital display, since engine speed varies continuously. In
addition, in certain tests it is necessary for the operator to find
an rpm peak or valley while making an adjustment to the engine.
This is far easier for the operator to visualize when displayed in
analog rather than digital form.
The use of analog panel meters, however, has several important
disadvantages. First, the accuracy of low cost analog panel meters
is not very good. Higher accuracy can be achieved with more
expensive panel meters, but this increases the overall cost of the
engine analyzer apparatus. Second, analog panel meters typically
must be dedicated to a particular function. As a result,
versatility of the meter is sacrificed, and cost is increased since
a different meter must be provided for each of several different
measurements which will be taken. Third, it is difficult to
indicate different ranges on an analog meter. When the measured
value is outside of the range of the meter, the operator must
manually change the range by a selector switch, and then must
decide which scale on the meter is to be used when viewing the
meter.
SUMMARY OF THE INVENTION
The present invention is an improved engine analyzer apparatus for
an internal combustion engine in which signals representing
operation of the engine are displayed in the form of a simulated
analog meter display. In the apparatus of the present invention,
analog input signals are digitized. Digital control means, which
preferably includes a programmed digital computer such as a
microprocessor, controls a point addressable digital display.
The digital control means causes the point addressable display to
display a visual depiction of an analog display, including a scale
and a pointer. Based upon the scale and the value of the digitized
input signal, the digitakl control means causes the point
addressable display to display the pointer so that the pointer has
its end point directed to a point on the scale corresponding to the
value of the digitized input signal. The digital control means
updates the point addressable display at a rate which is high
enough so that the pointer appears to move as the measured input
signal varies so as to simulate movement of a pointer of an analog
panel meter.
In preferred embodiments of the present invention, the digital
control means automatically selects the displayed scale of the
meter as a function of the digitized input signal. As a result, as
the value of the digitized input signal varies, the digital control
means automatically adjusts the scale of the displayed simulated
meter so that the pointer remains within the displayed scale.
In certain applications, the measured value must be maintained
within a predetermined range. In these cases, the digital control
means of the apparatus of the present invention preferably causes
the point addressable display to further display a shaded area
representing the range within which the pointer should be
maintained. The digital control means causes the point addressable
display to display data in two different "planes" which overlie one
another, but which are independent so that the pointer can move
within the shaded area.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view showing an engine analyzer apparatus
which utilizes the present invention.
FIG. 2 is an electrical block diagram of the engine analyzer
apparatus of FIG. 1.
FIG. 3 shows a cathode ray tube (CRT) display of the engine
analyzer apparatus of the present invention displaying a simulated
analog tachometer.
FIG. 4 shows the CRT display of FIG. 3 displaying the simulated
analog tachometer with a different scale from that shown in FIG.
3.
FIGS. 5A and 5B show the CRT display displaying a simulated analog
tachometer with a simulated movable pointer and a stationary shaded
range of desired operation.
FIG. 6 shows the CRT display displaying multiple simulated analog
meters simultaneously on the same screen.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In FIG. 1, engine analyzer 10 is shown. Mounted at the front of
housing 12 of analyzer 10 are point-addressable cathode ray tube
(CRT) raster scan display 14 and user interface 16, which is
preferably a control panel having a plurality of control switches
17A-17D, as well as a keyboard 17E for entering numerical
information. Extending from boom 18 are a plurality of cables which
are electrically connected to the circuitry within housing 12, and
which are intended for use during operation of the analyzer 10.
Timing light 20 is connected at the end of multiconductor cable 22.
"High tension" (HT) probe 24 is connected at the end of
multiconductor cable 26, and is used for sensing secondary voltage
of the ignition system of an internal combustion engine of a
vehicle (not shown). "No. 1" probe 28 is connected to the end of
multiconductor cable 30, and is used to sense the electrical signal
being supplied to the No. 1 sparkplug of the ignition system.
"Engine Ground" connector 32, which is preferably an alligator-type
clamp, is connected at the end of cable 34, and is typically
connected to the ground terminal of the battery of the ignition
system. "Points" connector 36, which is preferably an
alligator-type clamp, is attached to the end of cable 38 and is
intended to be connected to one of the primary winding terminals of
an ignition coil of the ignition system. "Coil" connector 40, which
is preferably an alligator-type clamp attached to the end of cable
42, is intended to be connected to the other primary winding
terminal of the ignition coil. "Battery" connector 44, which is
preferably an alligator-type clamp, is attached to the end of cable
45. Battery connector 44 is connected to the "hot" or "non-ground"
terminal of the battery of the ignition system. Vacuum transducer
46 at the end of multiconductor cable 47 produces an electrical
signal which is a linear function of vacuum or pressure, such as
intake manifold vacuum or pressure.
In the present invention, electrical signals derived from probes 24
and 28, from connectors 32, 36, 40 and 44, and from vacuum
transducer 46 are used to produce digital signals which are stored
as digital data in digital memory. Upon request by the user through
user interface 16, analyzer 10 of the present invention displays on
display 14 waveforms derived from selected stored digital data or
simulated analog meters, such as a tachometer, or alpha-numerical
messages or information.
FIG. 2 is an electrical block diagram showing engine analyzer 10 of
the present invention. Operation of engine analyzer 10 is
controlled by microprocessor 48, which communicates with the
various subsystems of engine analyzer 10 by means of master bus 50.
In the preferred embodiments of the present invention, master bus
50 is made up of fifty-six lines which form a data bus, an address
bus, a control bus, and a power bus.
Timing light 20, HT probe 24, No. 1 probe 28, Engine Ground
connector 32. Points connector 36, Coil connector 40, Battery
connector 44, and vacuum transducer 46 interface with the
electrical system of engine analyzer 10 through engine analyzer
module 52. As described in further detail in the previously
mentioned copending applications, which are incorporated herein by
reference, engine analyzer module 52 includes a digital section and
an analog section. Input signal processing is performed in the
analog section, and the input analog signals received are converted
to digital data. The digital section of engine analyzer module 52
interfaces with master bus 50.
Control of the engine analyzer system 10 by microprocessor 48 is
based upon a stored program in engine analyzer module 52 and a
stored program in executive and display program memory 54 (which
interfaces with master bus 50). Digitized waveforms and signals
produced, for example, by engine analyzer module 52 are stored in
data memory 56. The transfer of digitized waveforms and signals
from engine analyzer module 52 to data memory 56 is provided by
direct memory access (DMA) controller 58. When engine analyzer
module 52 provides a DMA Request signal on master bus 50, DMA
controller 58 takes control of master bus 50 and transfers the
digitized data from engine analyzer module 52 directly to data
memory 56. As soon as the data has been transferred, DMA controller
58 permits microprocessor 48 to again take control of master bus
50. As a result, the system shown in FIG. 2 achieves storage of
digitized waveforms and signals in data memory 56 without requiring
an inordinate amount of time of microprocessor 48 to accomplish the
data transfer.
User interface 16 interfaces with master bus 50 and preferably
includes keyboard 17E through which the operator can enter data and
switches 17A-17D through which the operator can select particular
tests or particular waveforms or meters to be displayed. When the
operator selects a particular waveform by means of user interface
16, microprocessor 48 retrieves the stored digitized waveform from
data memory 56, converts the digitized waveform into the necessary
digital display data to reproduce the waveform on raster scan
display 14, and transfers that digital display data to display
memory 60. As long as the digital display data is retained by
display memory 60, raster scan display 14 continues to display the
same waveform.
Display memory 60 contains one bit for each picture element (pixel)
that can be displayed on raster scan display 14. Each bit
corresponds to a dot on screen 14A of raster scan display 14. The
digitized waveform stored in data memory 56 preferably represents
individual sampled points on the waveform. Executive and display
program memory 54 includes a stored display program which permits
microprocessor 48 to "connect the dots" represented by the
individual sampled points of the digitized waveform, so that the
waveform displayed by raster scan display 14 is a reconstructed
waveform which has the appearance of a continuous analog waveform,
rather than simply a series of individual dots. Microprocessor 48
determines the coordinates of the dot representing one digitized
sampled point on the digitized waveform, determines the coordinates
of the next dot, and then fills in the space between the two dots
with additional intermediate dots to give the appearance of a
continuous waveform. The digital display data stored in display
memory 60, therefore, includes bits corresponding to the individual
sampled points on the waveform which had been stored by data memory
56, plus bits corresponding to the intermediate dots between these
individual sampled points.
As further illustrated in FIG. 2, engine analyzer 10 has the
capability of expansion to perform other engine test functions by
adding other test modules. These modules can include, for example,
exhaust analyzer module 62 and battery/starter tester module 64.
Both modules 62 and 64 interface with the remaining system of
analyzer 10 through master bus 50 and provide digital data or
digitized waveforms based upon the particular tests performed by
those modules. In the preferred embodiments shown in FIG. 2,
modulator/demodulator (MODEM) 66 also interfaces with master bus
50, to permit analyzer 10 to interface with remote computer 68
through communication link 70. This is a particularly advantageous
feature, since remote computer 68 typically has greater data
storage and computational capabilities that are present within
analyzer 10. Modem 66 permits digitized waveforms stored in data
memory 56 to be transferred to remote computer 68 for further
analysis, and also provides remote computer 68 to provide test
parameters and other control information to microprocessor 48 for
use in testing.
In certain tests and operations of engine analyzer 10, an analog
panel meter is more suitable than a digital display. One example is
that of a tachometer. Certain adjustments to be made by an operator
or technician require that the operator find an rpm peak or valley
as he makes the adjustment. Since engine rpm varies continuously as
an engine runs, reading a digital readout would be extremely
inconvenient and difficult for the operator.
The use of an analog panel meter tachometer, however, has
disadvantages. The accuracy of low cost panel meters is not very
good. In addition, versatility of the engine analyzer is sacrificed
by requiring specialized dedicated meters for particular functions.
It is also difficult to indicate different rpm ranges on an analog
tachometer, and the operator must often change ranges in order to
keep the meter needle within the range of the analog meter. This is
inconvenient, particularly when tests are being performed.
The present invention overcomes these inherent disadvantages of
analog panel meters by utilizing point addressable CRT raster scan
display 14, under control of microprocessor 48, to draw a simulated
analog meter. With the present invention, microprocessor 48
generates both the scale of the meter and the pointer which moves
as a function of the particular input signal received from the
engine analyzer module 52.
FIG. 3 shows display screen 14A of CRT display 14 in which
microprocessor 48 has generated a simulated analog tachometer
display. When this display mode is selected by the operator through
user interface 16, microprocessor 48 draws outline 300 of the
simulated meter, scale 302 (which includes a horizontal line,
vertical graduation lines, and numerical values adjacent the
graduation line), pointer 304, base line 306, and block 308
containing a digital display of engine rpm, and message 310. In the
embodiment shown in FIG. 3, pointer 304 has a fixed end point 304A
and a movable end point 304B. Movable end point 304B is positioned
along scale 302 at a point corresponding to the digital value of
engine rpm. This engine rpm value indicated by movable end pont
304B of pointer 304 corresponds to the digital rpm value displayed
in block 308. Microprocessor 48 also calculates intermediate points
between end points 304 and 304B, and fills in the dots (in a manner
similar to that described above with reference to simulated
waveforms) to provide an essentially straight line pointer 304
between ends point 304A and 304B. The engine rpm value used by
microprocessor 48 in generating the simulated tachometer is derived
from the signals produced by No. 1 probe 24. By appropriate timing
circuitry (not shown) within engine analyzer module 52, the engine
rpm is derived in the form of a digital value which is provided to
microprocessor 48 on a continual basis.
Microprocessor 48 updates CRT display 14 at a rate which is high
enough so that pointer 304 appears to move as the measured input
signal (in this case engine rpm) varies. As a result, the movement
of pointer 304 simulates the movement of a pointer of an analog
panel tachometer.
Microprocessor 48 generates pointer 304 by computing end point 304B
on scale 302 based upon the input rpm value. Since end point 304A
is fixed, and is effectively the pivot point of pointer 304,
microprocessor 48 has the information necessary to compute the
intermediate points between points 304A and 304B. Microprocessor 48
supplies the signals to display memory 60 which updates the
position of pointer 304.
As the new position of pointer 304 is drawn, microprocessor 48 also
causes display 14 to erase the previous position of pointer 304.
This requires that display memory 60 store both the new pointer
position and the previous pointer position so that the new pointer
is drawn as the old pointer is being erased. This avoids a
flickering effect each time the pointer position is updated.
As illustrated in FIG. 3, message 310 is preferably an alphanumeric
message which is based upon digital data from engine analyzer
module 52 or input data from user interface 16. In the particular
example shown, message 310 states "IGNITION TIMING+8.0
DEGREES".
The system of the present invention, which utilizes the point
addressable CRT display 14 to display a simulated meter, has
several important advantages over prior art engine analyzers which
use dedicated analog panel meters. First, the accuracy of the
simulated meter is very high, since there are no moving parts.
Second, the simulated analog meter function is very low in cost,
since it utilizes components of the analyzer system which are used
for other purposes, such as display 14, display memory 60, and
microprocessor 48. Third, the present invention is very versatile,
since any one of a variety of different meters can be simulated on
the same display screen 14, simply by changing the scale and legend
being displayed, and controlling the pointer as a function of a
different input signal. Fourth, the size of the simulated analog
meter can be much larger than conventional panel meters used in
engine analyzers. As shown in FIG. 3, the meter fills almost the
entire screen 14A of display 14. This allows the meter to be read
from a much greater distance.
Another important advantage of the present invention is illustrated
in FIG. 4. In this figure, a simulated meter similar to that shown
in FIG. 3 is shown, and similar elements are designated by similar
numerals. In FIG. 4, however, a different scale 302' is used, since
a higher rpm value is being sensed and displayed. In FIG. 3, scale
302 ranges from 0 to 1,000 rpm, while in FIG. 4 scale 302' ranges
from 0 to 3,000 rpm. In preferred embodiments of the present
invention, microprocessor 48 automatically switches the scale of
the simulated meter as a function of the input signal. As the
digital input signal (for example rpm) approaches the upper end of
the scale, microprocessor 48 automatically redraws the scale with a
larger range. Similarly, when the input signal drops to a
predetermined level, microprocessor 48 shifts range and redraws the
scale automatically to reflect a lower range, so that a maximum
resolution of the meter is maintained. This automatic changing of
scales is performed without requiring operator intervention, as is
required with prior art analog panel meters. In addition, since
only a single scale is displayed at any one time, the operator does
not have problems in interpreting the meter and selecting which
scale should be used.
FIGS. 5A and 5B illustrate another preferred embodiment of the
present invention. In this embodiment, the meter displayed on
display screen 14A includes a shaded area 312, which represents a
window within which the pointer 304 should remain while a test is
being performed.
As illustrated in FIG. 5A, pointer 304 is outside of the desired
window 312. In FIG. 5B, pointer 304 is within window 312. Pointer
304 is written by microprocessor 48 independently of window 312.
This requires the capability of CRT display 14 being able to write
in two "planes" which are independent of one another. In other
words, the window 312 is drawn in an "A Plane" while pointer 304 is
written in a "B Plane". These two planes are displayed essentially
simultaneously, but the movement of the pointer 304 to various
positions is independent of the position of window 312. Under the
control of microprocessor 48, the A and B planes are effectively
overlayed on display screen 14A. Pointer 304 does not interfere
with window 312, since they are stored in different areas of
display memory 60. Window 312 is drawn first, before pointer 304.
Microprocessor 48 calculates end points on scale 302' based upon
the desired window range. This window range may be stored in
memory, or may be provided by the operator through user interface
16. By using the two end points of window 312 on scale 302' and end
point 304A (which is the pivot point of pointer 304),
microprocessor 48 draws in the lines between point 304A and end
points 312A and 312B. Microprocessor 48 then uses a filler routine
to fill in the area between the two lines in a "half tone" fashion
to give a shaded background appearance. Finally, microprocessor 48
draws pointer 304 in the manner previously described in reference
to FIGS. 3 and 4. Pointer 304 is updated at a rate which gives an
apparent movement of the pointer as a function of the input signal,
as if the window did not exist.
The embodiment illustrated in FIGS. 5A and 5B further illustrate
the great versatility of the present invention. The position and
size of window 312 is adjustable, and can be varied by the operator
or varied automatically. The particular position and size of window
312 can be varied from meter-to-meter and from test-to-test without
requiring a large number of individual costly analog panel
meters.
FIG. 6 illustrates still another advantage of the present
invention. Although the previous embodiments have shown a single
meter being displayed on display screen 14, the present invention
also permits the display of multiple meters simultaneously, so the
operator can monitor several parameters at one time. In the
embodiment shown in FIG. 6, three individual simulated meters 320,
330 and 340 are displayed on display screen 14A.
Although the specific examples shown in the figures involve a
simulated tachometer, other functions performed by engine analyzer
10 also are well adapted to simulated analog meter displays. For
example, meters 320, 330 and 340 are in one embodiment, voltmeters
or ammeters showing voltage or current at different measured points
of the electrical system of the engine under test. In another
embodiment, the outputs of exhaust analyzer module 62 also are
capable of being displayed by meters 320, 330 and 340. In each
case, the operation of CRT display 14 under the control of
microprocessor 48 is similar to that described with reference to
the tachometer shown in FIGS. 3, 4, 5A and 5B.
In conclusion, the present invention is a highly advantageous
digitally based engine analyzer apparatus which eliminates the need
for dedicated analog panel meters, while still providing the
operator with the useful information normally provided by analog
meters. The present invention provides simulated analog meters on a
point addressable display, and provides a variety of different
display modes which are either impossible or difficult to achieve
with conventional analog meters.
Although the present invention has been described with reference to
preferred embodiments, workers skilled in the art will recognize
that changes may be made in form and detail without departing from
the spirit and scope of the invention.
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